Keep on writing something like this.

main.go

package main

import (
	"bytes"
	"io"
	"log"
	"net/http"
)

type LogHandler struct {
	logChan chan *bytes.Buffer
}

func (l LogHandler) ServeHTTP(writer http.ResponseWriter, request *http.Request) {
	b := bytes.NewBuffer(nil)
	request.Write(b)
	io.Copy(b, request.Body)
	l.logChan <- b

}

func main() {
	logChan := make(chan *bytes.Buffer)
	go func() {
		for b := range logChan {
			log.Printf("==================\n%s\n\n==============", b.String())
		}
	}()
	http.ListenAndServe(":9090", &LogHandler{logChan: logChan})
}